Aliphatic 1,3-diols, particularly 1,3-propanediol (1,3-PDO), have many applications as monomer units for polyester and polyurethane, and as starting materials for the synthesis various value-added products. 1,3-propanediol was chemically produced either from acrolein or ethylene oxide a petroleum feedstocks. However, as non-renewable crude oil resources become limited, substitutes for petroleum feedstocks are increasingly sought after; as such the synthesis of 1,3-propanediol from renewable resources is of great interest. The non-renewable crude oil resources were used as feedstock chemicals. However, considering the serious concern over the dwindling non-renewable petroleum feedstocks and environmental factors an alternative methods based on renewable resources are of immense interest and highly attractive.
U.S. Pat. No. 5,030,771 disclosed a method of producing aliphatic and cycloaliphatic diols by catalytic hydrogenation of dicarboxylic acid esters under very harsh conditions (higher temperature and higher pressure) by the use of a copper chromite catalyst, wherein said dicarboxylic acid ester has up to 12 carbon atoms in the diacid portion and up to 4 carbon atoms in the alcohol portion.
U.S. Pat. No. 5,406,004 disclosed a process for the production of alcohols and diols by hydrogenation of a corresponding hydrogenatable material selected from monoesters of carboxylic acids, monoesters of dicarboxylic acids, diesters of dicarboxylic acids, lactones, and mixtures of two or more thereof, wherein said catalyst is selected from reduced manganese promoted copper catalysts, reduced copper chromite catalysts, reduced promoted copper chromite catalysts, and chemically mixed copper-titanium catalysts.
Article titled “New CNN-Type Ruthenium Pincer NHC Complexes. Mild, Efficient Catalytic Hydrogenation of Esters” by E Fogler et al. published in Organometallics, 2011, 30 (14), pp 3826-3833 reports New pincer ruthenium complexes (2-6) based on the new bipyridine-NHC ligand 1 resulting in an efficient catalytic hydrogenation of esters to the corresponding alcohols under mild conditions. However, this strategy was not applicable to hydrogenation of terminal diesters to terminal diols.
Article titled “Electron-Rich PNP- and PNN-Type Ruthenium(II) Hydrido Borohydride Pincer Complexes. Synthesis, Structure, and Catalytic Dehydrogenation of Alcohols and Hydrogenation of Esters” by J Zhang et al. published in Organometallics, 2011, 30 (21), pp 5716-5724 reports Electron-rich phosphorus ligand based PNP- and PNN-type ruthenium(II) hydrido borohydride pincer complexes, [RuH(BH4)(tBu-PNP)] (tBu-PNP=(2,6-bis(di-tert-butylphosphinomethyl)pyridine) (5) and [RuH(BH4)(tBu-PNN)] (tBu-PNN=2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) (6), were prepared from their corresponding N2-bridged dinuclear Ru(II) complexes [(tBu-PNP)RuCl2]2(μ-N2) (3) and [(RtBu-PNN)RuCl2]2(μ-N2) (4), respectively. The 6 effectively catalyzes the hydrogenation of nonactivated aromatic and aliphatic esters to the corresponding alcohols with TON˜200 under a relatively mild pressure of dihydrogen and neutral and homogeneous conditions.
Article titled “Efficient hydrogenation of biomass-derived cyclic di-esters to 1,2-diols” by E. Balaraman et al. published in Chem. Commun., 2012, 48, 1111-1113 reports an unprecedented homogeneous hydrogenation of cyclic di-esters, in particular biomass-derived glycolide and lactide, to the corresponding 1,2-diols catalyzed by Ru(II) PNN (1) and Ru(II) CNN (2) pincer complexes under mild hydrogen pressure. This strategy is applicable only for cyclic esters (easy to hydrogenate under optimal conditions).
Article titled “Ester hydrogenation catalyzed by Ru—CNN pincer complexes” by Y Sun et al. published in Chem. Commun., 2011, 47, 8349-8351 reports new Ru—CNN pincer catalysts for ester hydrogenation under mild conditions. They synthesized and characterized two new NHC-based CNN-pincer ligands and the corresponding ruthenium (II) complexes 2. Complex 2a can be deprotonated by a strong base to form a 5-coordinate species 3a With dearomatized pyridine moiety in the ligand backbone. Compound 3a can split H2 to form a trans-dihydride species 4a with a rearomatized pyridine moiety in the ligand back-bone.
PCT application no. 2006106484 disclosed a process for the reduction by hydrogenation, using molecular H2, of a C3-C7O substrate containing one or two esters, or lactones, functional groups into the corresponding alcohol, or diol, characterized in that said process is carried out in the presence of a base and at least one catalyst or pre-catalyst in the form of a ruthenium complexes of a tetradentate ligand wherein the coordinating groups consist of at least one amino or imino group and at least one phosphino group.
U.S. Pat. No. 6,232,511 disclosed a process for the production of 1,3-propanediol comprising: hydrogenating an aqueous solution of 3-hydroxypropionaldehyde in the presence of a heterogeneous catalyst, the hydrogenating being carried out at a temperature of from 30° C. to 180° C., a hydrogen pressure of 5 to 300 bar and a pH of from 2.5 to 7.0, wherein the catalyst is a supported catalyst comprising an oxide phase on which ruthenium is disposed in a quantity of from 0.1 to 20 wt %, relative to the oxide phase.
Article titled “catalytic Hydrogenation of Esters. Development of an Efficient Catalyst and Processes for Synthesizing (R)-1,2-Propanediol and 2-(1-Menthoxy)ethanol” by W Kuriyama et al. published in Org. Process Res. Dev., 2012, 16 (1), pp 166-171 reports a ruthenium catalyst for the reduction of esters by hydrogenation to (R)-1,2-propanediol and 2-(1-menthoxy)ethanol.
Article titled “Ruthenium-catalyzed hydrogenation of esters using tripodal phosphine ligands” by M J Hanton et al. published in Journal of Molecular Catalysis A: Chemical, 2011, 346 (1-2), pp 70-78 reports the synthesis of a new tripodal phosphine ligand, N(CH2PEt2)3, N-TriPhosEt and the use of tripodal ligands of this type, N(CH2PR2)3 (R=Ph, Et), in conjunction with ruthenium for the catalyzed hydrogenation of dimethyl oxalate (DMO). However complete hydrogenation is difficult.
Article titled “Synthesis of alcohols and diols by hydrogenation of carboxylic acids and esters over Ru—Sn—Al2O3 catalysts” by M Toba et al. published in Applied Catalysis A: General, 1999, 189 (2), pp 243-250 reports new sol-gel Ru—Sn—Al2O3 catalysts prepared by a complexing agent-assisted sol-gel method, which selectively hydrogenates unsaturated or aromatic carboxylic acids and their esters to the corresponding unsaturated or aromatic alcohols at low pressure.
Article titled “Hydrogenation of dimethyl adipate over bimetallic catalysts” by SM Santos et al. published in Catalysis Communications, 2004, 5 (7), pp 377-381 reports hydrogenation of dimethyl adipate at moderate conditions (5 MPa and 255° C.) aiming at screening the performance of noble metals and some additives on 1,6-hexanediol selective production. Ruthenium was found to be the most active metal and selectively cleavage the O—CH3 bond in the ester group giving the adipic acid monomethyl ester. The production of hexanediol was significant over RuSn/Al2O3 catalyst (49% selectivity).
U.S. Pat. No. 6,844,452 disclosed a process for the co-production of butane-1,4-diol and tetrahydrofuran by hydrogenation of a corresponding hydrogenatable material selected from mono-(C1 to C4 alkyl) esters of dicarboxylic acids, di-(C1 to C4 alkyl) esters of C4 aliphatic dicarboxylic acids, γ-butyrolactone, and mixtures of two or more thereof.
U.S. Pat. No. 3,314,987 disclosed a process for catalytically reducing perfluorinated diesters having the general formula ROOC(CF), COOR, wherein R is a lower alkyl radical, and n is a positive integer having a value of from 2 to 4, inclusive, which process comprises reacting said perfluorinated diester with hydrogen at pressures of from about 8000 to more than 16,000 p.s.i. and temperatures of from about 50-300° C., in the presence of from 20% to 300% by weight, based on the weight of the perfluorinated diester, of a copperchromium oxide catalyst essentially free of uncombined alkaline earth oxide.
U.S. Pat. No. 4,751,334 disclosed a process for the production of butane-1,4-diol by vapor phase hydrogenolysis of a dialkyl ester of a C4 dicarboxylic acid in presence of heterogeneous hydrogenolysis catalyst comprises copper chromite.
U.S. Pat. No. 8,846,983 disclosed a method for reducing a halogenobenzoic acid ester, in which dehalogenation is inhibited in presence of a ruthenium complex represented by the following general formula (1): RuXY(CO)(L)

U.S. Pat. No. 8,471,048 disclosed a ruthenium carbonyl complex that is represented by Formula (1): RuXY(CO)(L) (1) wherein X and Y, which may be the same or different from each other, represent an anionic ligand and L represents a tridentate aminodiphosphine ligand represented by Formula (2):
wherein R1, R2, R3, and R4, which may be the same or different from each other, represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkyloxy group, a cycloalkyloxy group, an aryloxy group, an aralkyloxy group, a heterocyclic group, or a substituted amino group, and R1 and R2 or R3 and R4 may bind to each other to form a ring with an adjacent phosphorus atom, the alkyl group, cycloalkyl group, aryl group, aralkyl group, alkyloxy group, cycloalkyloxy group, aryloxy group, aralkyloxy group, heterocyclic group, and substituted amino group may have a substituent group, and Q1 and Q2, which may be the same or different from each other, represent a divalent alkylene group which may have a substituent group, a divalent cycloalkylene group which may have a substituent group, or a divalent aralkylene group which may have a substituent group.
Article titled “Bond Activation and Catalysis by Ruthenium Pincer Complexes” by C Gunanathan et al. published in Chem. Rev., 2014, 114 (24), pp 12024-12087 reports a review on ruthenium pincer complexes of type B (saturated) and C (unsaturated) developed since 2003 from the perspective of bond activation and catalysis.
Article titled “Homogeneous hydrogenation of fatty acid methyl esters and natural oils under neat conditions” by N T Fairweather et al. published in Organometallics, 2015, 34 (1), pp 335-339 (Publication Date (Web): Dec. 18, 2014) reports a series of ruthenium- and iron-based pincer catalysts for the homogeneous hydrogenation of fatty acid methyl esters to fatty alcohols with turnover numbers (TONs) of up to 1860. These catalysts operate under neat conditions (no solvent) from the gram to the kilogram scale.
U.S. patent application no. 2015329455 disclosed a process for the production of α,α-difluoroacetaldehyde involves reacting α,α-difluoroacetic acid esters with hydrogen gas (H2) in the presence of a ruthenium catalyst represented by the general formula [2],

Article titled “Osmium and Ruthenium Catalysts for Dehydrogenation of Alcohols” by M Bertoli et al. published in Organometallics, 2011, 30 (13), pp 3479-3482 reports a series of pincer-type complexes of Os and Ru and investigated in catalytic alcohol dehydrogenation. The hydrides OsHCl(CO)[HN(C2H4PiPr2)2] and OsH2(CO)[HN(C2H4PiPr2)2] possess good air, moisture, and thermal stability and are outstanding versatile dehydrogenation catalysts for primary alcohols for reactions of transfer hydrogenation, dehydrogenative coupling, and amine alkylation.
PCT application no. 2014036650 disclosed a novel amino-sulfide metal catalyst for organic chemical syntheses including hydrogenation (reduction) of unsaturated compounds or dehydrogenation of substrates. The range of hydrogenation substrate compounds includes esters, lactones, oils and fats, resulting in alcohols, diols, and triols as reaction products.
Article titled “High Productive Ethylene Trimerization Catalyst Based on CrCl3/SNS Ligands” by E Ahmadi et al. published in Catalysis Letters, 2011, 141 (8), pp 1191-1198 reports Methylaluminoxane (MAO)-activated chromium (III) complexes of tridentate SNS ligands of the form (RSCH2—CH2)2NH (R=alkyl, aryl) have been prepared and tested for the trimerization of ethylene to 1-hexene.
Article titled “Replacing Phosphorus with Sulfur for the Efficient Hydrogenation of Esters” by D Spasyuk et al. published in Angew Chem Int Ed Engl., 2013, 52(9), pp 2538-42 reports readily available, air-stable amino-sulfide catalyst, [RuCl(2)(PPh(3)){(HN(C(2)H(4)SEt)(2)}]. This complex displays outstanding efficiency for the hydrogenation of a broad range of substrates with C═X bonds (esters, ketones, imines), as well as for the acceptorless dehydrogenative coupling of ethanol to ethyl acetate.
The terminal esters are difficult to hydrogenate. The production of terminal diols in one step with improved yield, minimal impurities and by products which requires a catalyst system with good stability both during terminal diols synthesis and during product recovery and recycle. Therefore, it is desirable in the art to identify alternative catalyst systems that demonstrate potential advantages in the one-step production with improved yield of terminal diols.